Pandoravirus, bigger and unlike anything seen before

The discovery of the giant Mimivirus and Megavirus amazed virologists (and also many others). Their virions (750 nanometers) and DNA genomes (1,259,000 base pairs) were the biggest ever discovered, shattering the notions that viruses could not be seen with a light microscope, and that viral genomes were smaller bacterial genomes. Now two even bigger viruses have been discovered, which are physically and genetically unlike any previously known viruses. They have been called Pandoraviruses. Both new viruses were isolated by culturing environmental samples in the amoeba Acanthamoeba castellani. Pandoravirus salinus was isolated from shallow marine sediment in a river at the coast of central Chile, and Pandoravirus dulcis was obtained from mud at the bottom of a freshwater pond near Melbourne, Australia. The P. salinus genome is at least 2.77 megabases in length (there is some uncertainty in the actual length due to the presence of repeated sequences at the ends of the DNA), while the P. dulcis genome is 2.47 megabases in length. The smaller P. dulcis genome is a subset of the P. salinus genome. These new genomes are twice as large as those of previously described viruses, and bigger than the genomes of intracellular bacteria such as Tremblaya (138,927 base pairs) and Rickettsia (1,111,523 bp). They are smaller than genomes of free living bacteria (Mycobacterium, 3,268,203 bp) or protists (Babesia, 8,200,000 bp) but larger than many genomes of free living Arc...
Source: virology blog - Category: Virology Authors: Tags: Basic virology Information amoeba DNA genome megavirus mimivirus Pandoravirus viral Source Type: blogs